Light-induced protein and lipid oxidation in cheese: Dependence on fat content and packaging conditions

Photo-oxidation of cheese products has become an issue due to the fact that packaging of cheeses in transparent materials is very frequently used. The present study aimed to investigate the effect of fat content and availability of oxygen on light-induced oxidation in cheese, as we expected that the fat content would affect the oxidation pathways. Two different model cheeses with 5.4% and 18% fat were packed in air and in vacuum, respectively. The contents of protein (dityrosine and dimethyl disulphide (DMDS)) and lipid (lipid hydroperoxides, pentanal, hexanal and heptanal) oxidation products were significantly reduced in vacuum-packed cheeses compared to cheeses packed in air. Protein oxidation correlated to the concentration of lipids in the cheeses, and interactions between the lipid radicals and proteins seemed to be decisive for the generation of dityrosine, whereas the influence of lipid radicals on the generation of the DMDS seemed more ambiguous. The higher levels of dityrosine and DMDS in the cheese with a high fat content indicated that transfer of radicals from the lipids to the proteins occurred. Even though the generation of DMDS was reduced in vacuum-packed cheese when compared to cheese packed in air, DMDS was formed in vacuum-packed cheese.